Algae is a common problem for most pool and spa owners, especially in the beginning when trying to get the chemistry right and keep the water clean.

And algaecide is one of those chemicals you might not even realize you need until you have a few battles with those nuisance spores yourself.

The problem with algae is that it’s fast-growing, fast-spreading, and sometimes hard to eliminate. Chlorine does the trick in a lot of cases, but you’ll almost always need a little something extra to kick it to the curb.

That’s where algaecide comes in. It’s not necessarily a cure-all, but when used properly, it’s a good assistant to your regular chemicals.

The question now is which algaecide to use. If you’re a new pool-owner, you probably haven’t had much experience with any of the chemicals and you need a little guidance.

And that’s exactly what we are here to give you! Take a look at our top picks for the ten best. You really can’t go wrong with any of them.

#2. hth Pool Algaecide Super Algae Guard

This is a good algaecide to use if you’re battling less common algae, such as black or yellow. It does knock out green algae as well, but it’s designed to fight even stronger stuff.

Aside from being stronger than a lot of other algaecides, hth Super Algae Guard is an excellent preventative treatment that lasts 90 days after treatment. But it’s also surprisingly safe to swim in immediately after application.

#3. Clorox Pool & Spa Algaecide + Clarifier

Many times when you treat algae, you also need to use a clarifier to clear up the water. Clorox’s Pool&Spa Algaecide + Clarifier does it all.

Just like the first Clorox algaecide we mentioned, this one is safe for all types of pools. It’s also most effective on green algae, and does a beautiful job of removing the cloudiness all that junk can cause.

In the Swim’s Super Pool Algaecide lives up to its name. This product is super concentrated and super powerful when it comes to knocking out all types of algae in all types of water.

The active ingredient in this algaecide is copper, which has proven to be a quick and powerful agent for killing algae spores and preventing growth. This same ingredient does make it unsafe for drinking or well water however, so just make sure you’re only using it where you swim!

#7. SeaKlear 90-Day Algae Prevention & Remover

SeaKlear offers a 90-day guarantee with its algaecide, meaning you won’t see any algae in your pool for at least three months. This is, of course, provided that you follow the directions and use it correctly.

This product does contain copper, so it’s effective against green, blue-green, black, and mustard algae. It also won’t foam or stain your pool surfaces, no matter what type you have.

#8. Pool Mate Swimming Pool Algaecide

This algaecide is non-metallic, yet effective on all types of algae, including pink, which is less common and difficult to kill. It also works wonders on other types, though, and with very little effort.

With Pool Mate’s algaecide, your family can jump in the pool within 15 minutes of treatment. It’s effective, non-staining, concentrated, and completely safe for all pool surfaces.

#10. Kem-Tek Algaecide

Kem-Tek Algaecide not only eradicates algae. It also clarifies the water and prevents future infestations.

What sets this product apart is that it’s the highest-strength polymer algaecide available for pool use. This makes it excellent for algae that has proven resistant to your other treatments.

Because it is so strong, however, use caution with it. Follow the manufacturer’s instructions for application and don’t swim in it until it’s completely safe.

What is Pool Algae?

Pool algae are actually living organisms that contain chlorophyll and use photosynthesis to grow. It’s not technically classified as a plant, but can be most closely identified that way because of the way it grows and multiply.

Algae is often thought to linger in warm, dark places, but it actually flourishes more in the sunlight. It also needs food to survive and finds nourishment in all kinds of contaminants. Some examples would be debris, dissolved beauty products, and dust.

Algae can accumulate in pools by being brought in, but a little of it is almost always present, looking for a chance to attach to something and bloom. That’s why chlorine and pH levels are so important in proper pool maintenance. It keeps those spores at bay, giving them little opportunity to grow.

Of course, you might be wondering why it matters. After all, algae itself never really hurt anybody, right?

Since algae thrives on debris and waste, you can just imagine what types of things can lurk there. To name just a few, fecal matter, blood, mucus and saliva.

Unpleasant, I know.

And within these pieces of matter and fluids can live a whole host of bacteria. E. coli, giardia, legionella, shigella, campylobacter, and salmonella are just a few.

A well-balanced pool with the right amount of chlorine usually takes care of the bad stuff, but algae can hang on to it. Not to mention the fact that algae also uses up the chlorine, making it almost impossible to balance.

And once you let a little algae start to make its home in your pool, it will spread and grow, and quickly take over. That’s when you have a real mess on your hands.

Different Types of Algae

All algae is not created equal, and there are actually more than 20,000 known species of it. But the ones most commonly found in pools are green, black, yellow, and pink.

Green Algae

Green algae, scientifically known as chlorophyta, is the most common type of pool algae. If you own a pool, you’ll undoubtedly see it from time to time, no matter how hard you try to keep it out.

Not only does it show up in pools, but it can also be a problem in wells, ponds, and other natural bodies of water.

You’ll first start to notice it in tiny clusters on the corners of your pool steps or corners. And if you don’t get rid of algae right away, it will grow to a noticeable size within 24 hours.

If you catch it quickly, you can usually scrub it off and add an algaecide to kill it. But in most cases, you’ll also want to shock your pool to completely eradicate it and its invisible spores. (Check out our guide for how to clean a green pool).

Black Algae

Of all the types of algae, black algae is the hardest to get rid of. It’s super resistant to chlorine and tends to leave the worst stains.

Black algae is technically a type of green algae, but it contains compounds that mask the color. These same compounds also form a protective barrier around the organism, helping it resist chlorine and other chemicals.

If you end up with a black algae infestation, you can get rid of it, but it will probably take you a while.

Yellow Algae

You’ll also hear yellow algae called mustard algae because of the dark mustard color. It’s most often found in the shade as it needs less sunlight than the others to grow.

Yellow algae is also more difficult to deal with than green algae, but it’s a little less invasive than black. It is, however, prone to re-infestation because it tends to hang on to pool toys and small corners of the filter.

Like black algae, this species is resistant to chlorine, so you’ll have to be persistent in scrubbing and treating it.

Pink Algae

Pink algae might sound pretty, but it’s actually a slimy, bacteria that’s resistant to chemicals. In fact, it’s that slime that protects it from chemicals that would kill it.

Pink algae thrives in dark areas with slow moving water, so lots of sunlight and good water circulation is the best prevention.

How Does Algaecide Work?

Algaecides should be used as part of your regular pool maintenance in order to kill active spores and prevent new blooms from taking root. But they can’t do the job all on their own.

The most effective way to keep algae at bay is by maintaining the right pool chemistry. Your pH and chlorine levels are the most important part of the process. But what a good algaecide should do is work alongside these chemicals to deliver the most effective results.

The first thing the algaecide does is to bust up the algae cells, preventing the plant from blooming. But if it has already bloomed, it does the same thing, killing the thriving organism.

It’s important to note that just as there are different types of algae, there are also different types of algaecide to treat it.

What to Consider When Buying Algaecide

There are a couple of things to consider when choosing your algaecide, but the most important is the type of algae you’re treating.

Type of Algae

You’ll notice that a few of the products we listed earlier contain copper, which is an effective ingredient on black algae and others that are hard to kill. It will also knock out the other types, but it may be a harsher chemical than you need if you’re just dealing with green algae.

Most other algaecides are ammonia-based. These are great for green algae or very small infestations of others. But they don’t work great on black or yellow.

Price

Of course, price is usually a consideration for anything we buy. But most algaecides are extremely affordable and last quite a while.

I would urge you not to skimp on this product, however. For a relatively reasonable amount of money, you could save yourself some major headaches down the road.

Long-Lasting

Also, look for a product that’s long-lasting. We usually only recommend the ones that will kill and prevent algae for at least 90 days. But if you have a problem with a hard-to-kill variety, you’ll be using it more often anyway.

Stain-Free

Stain-free and non-foaming are important factors to most people in algaecides. The ones that contain copper can sometimes stain your pool surface, but this may be unavoidable if you have a bad infestation.

And the foam some of them cause may not be harmful, but it’s certainly unpleasant to swim in.

Clarifier

Most algaecides will cause the water to be a bit cloudy after use. It doesn’t hurt anything, but it’s definitely not pretty.

8 Tips for Protecting Your Pool Against Algae

Keep your water circulating. Algae thrives in still water, so making sure yours is always moving is a must for preventing it. This means running your pool pump regularly, especially after brushing and cleaning.

Maintain your filtration system. It’s extremely difficult to keep spores out 100% of the time since they latch on to swimmers and pool toys. So, keep your pool filter clean to make sure they’re doing most of the work for you.

Keep your pool balanced. Once a week is the minimum number of times you should be testing your pool chemistry. But if you’ve had inclement weather, large amounts of swimmers, or an outbreak of algae, you should test and balance it daily.

Shock your pool regularly. Shocking your pool will help reset it to normal levels. Doing this weekly is ideal, but once a month should be an absolute requirement.

Clean your pool all year. Just because you’re not using it doesn’t mean it isn’t collecting waste and growing algae. Clean out debris and test your filtration system regularly. Also, make sure you’ve shocked it properly before closing it up for the winter.

Brush your pool often. Many pool-owners only brush their pools when there’s a problem. But if you add it to your regular maintenance regime before vacuuming, you’ll be less likely to deal with algae.

Use a vacuum. Speaking of vacuuming, don’t neglect this task! Keeping your surfaces free of debris and spores goes a long way toward a problem-free pool.

Use algaecide regularly. Yep, that’s where we were going with this post. Using algaecide as part of your regular maintenance routine can not only kill active plants, but prevent spores from blooming.

Algaecide FAQ

Can you put too much algaecide in your pool?

Absolutely! Just like with any chemical, there’s an ideal amount you should use in any given situation.

Too much algaecide can cause foaming, skin irritation, and sometimes staining. Of course, each effect depends on the formulation.

Does algaecide affect chlorine?

Algaecide does not directly affect any of your pool chemistry levels, but algae does. That means that once you’ve effectively killed off the algae, you may have to adjust your chemistry levels again.

Can I use pool shock and algaecide together?

It’s not a good idea. Too much chlorine will neutralize the ingredients in your algaecide, rendering it useless. It’s better to add algaecide once your chlorine levels are back to normal.

Can too much algaecide make a pool cloudy?

It certainly can. The cloudy effect is harmless but it can certainly make the water unappealing to swimmers.

That’s why many algaecides also contain clarifiers, but if they don’t, you can always use one separately.

Bottom Line

Keeping algae out of your pool can be a constant battle. But the more you stay on top of it, the easier your life will be.

Most pool-owners find that chlorine alone is not enough to do the trick, especially once they’ve had a few algae blooms. But adding algaecide to your routine is probably the best way to combat the nuisance.

Try one of our recommended products and let us know what you think. We’re always looking out for fresh reviews!